Machine for producing spherical surfaces



June 3, 1958 A. H. WHITE MACHINE FOR PRODUCING SPHERICAL .SURFACES FiledMarch 21, 1956 7 Sheets-Sheet l June 3, 1958 A. H. WHITE 2,836,939

MACHINE FOR PRODUCING SPHERICAL SURFACES Filed March 21, 1956 vSheets-Sheet 2 /v PEA/72m June 3, 1958 A. H. WHITE 2,836,939

' MACHINE FOR PRODUCING SPHERICAL SURFACES Filed March 21, 1956 7Sheets-Sheet 3 A an/m flaw/v17 Mrs June 3, 1958 A. H. WHITE 2,836,939

MACHINE FOR PRODUCING SPHERICAL SURFACES Filed March 21, 1956 7Sheets-Sheet 4 M1 X I3 R U j 49 A. H. WHITE 2,836,939

7 Sheets-Sheet 5 R mm am m V 0 0o ov m June 3, 1958 MACHINE FORPRODUCING SPHERICALv SURFACES Filed March 21, 1956 i I I MIL v June 3,1958 wHlTE 2,836,939

MACHINE FOR PRODUCING SPHERICAL SURFACES Filed March 21, 1956 '7Sheets-Sheet 6 June 3, 1958 A. H. WHITE MACHINE FOR PRODUCING SPHERICALSURFACES 7 Sheets-Sheet '7 Filed March 21, 1956 WVEAIIVIQ #1? 174m Ab/may MHTE Ar-raatrvf7 Unite States MACHINE FOR PRODUEZNG SPHERE'CALSURFACES Arthur Howard White, Stourhridge, Engiaud Application March 21,1956, Serial No. 57255? Claims priority, application Great Eritain March24, 1955 11 Claims. (Cl. Si -131) This invention is concerned with a newmachine for producing spherical surfaces such, for example, aspartspherical ends or heads on rods and spindles, or partsphericaiconcave seatings, by any machining process such as milling, grinding,lapping or the like.

One method used at present for producing a spherical end on a rod is touse a form tool ground to the required radius and fed in a right anglesto the axis of rotation of the work-piece. This method sufiers from anumber of obvious disadvantages. The feed must be stopped at exactly theright point from the axis of rotation or the sphere will be oblate. Onetool Will produce a sphere of only one diameter. The rotation of thecomponent gives a cutting speed which varies from a maximum at the topdiameter to zero at the axis. Furthermore, the truth of the sphere, evenif the feed-in is correct, is dependent wholly on the accuracy of theform tool, and any irnperfections in its edge will leave rings orgrooves on the Work. Again, if the tool is a formed grinding wheel, theload on its bearings is wholly transverse to its axis of rotation andany play in the bearings will give rise to trouble.

Another method, more generally used, overcomes some, but not all, of thedisadvantages of that described above. This is to move the tool in anare about the centre of the desired sphere whilst the work is rotatedabout an axis passing through that centre. However, there is stillpresent the disadvantage of varying cutting speed, and there is now theadded drawback that the tool or grinding wheel has only point contactwith the Work and will consequently wear rapidly. The resultant groovein the tool or wheel will then, it is true, give line contact with thework, but this will then be incorrect for any subsequent work with adifferent radius of curvature. If it were possible to maintain thesurface of the tool truly fiat, the spherical surface would presentunder a microscope a spiral of minute fiat surfaces. As the tool-holdermust move in an arcuate path, it is di ficult, if not impossible, to fitat the same time a progressive inward eed.

In this second method, the accuracy of the sphere is dependent on thefreedom from play of the pivot about which the tool-holder moves. Yetthis pivot must be free enough to allow smooth and steady movement, asany interruption or hesitation in the travel of the tool will produce aring or groove on the work. Where tool is a grinding wheel, the grindingload produces opposite sideway loads, on the two bearings of thegrinding spindle. All these are potential sources of vibration whichgive rise to errors in the truth of the sphere produced.

it is known in the glass industry to advance a rotating work-piece, suchas a lens, towards a rotating grinding wheel, the axis of which makes anangle with that of the work. However, it is evident that this methodcannot be used to produce surfaces of more than a hemisphere;furthermore, and this is a particularly important point, it is virtuallyimpossible to make the surface with 2,335,939 Patented June 3, 1958 acentre at an accurately predetermined point relative to the workpiece.

According to the present invention, a spherical surface is produced on awork-piece by rotating it about an axis and advancing towards it a toolrotating about a second axis intersecting but not parallel to the first,the line of advance of the tool being along the second axis. The

entre of the surface produced will be the point of intersection of thetwo axes and its sphericity will be virtually prefect. The tool may havea single cutting point or may be a circular edge or a cutter with aseries of teeth arranged in a circle, with its centre on and its planeperpendicular to its axis of rotation.

If the surface to be produced is to include a part passing through theaxis of rotation of the work-piece, as would be the case in a ball endon a rod, then the ad- Vance must stop at the point where the circularpath of the tool just passes through the axis of rotation of thework-piece. Then, as the axial position of the work is fixed duringmachining and the tool advances along a fixed line to a predeterminedpoint, it is possible to control very accurately the size and positionof the surface produced.

Where the sphere is to be ground, the tool may be a iollow cylindricalgrinding wheel, the inner edge of which makes contact with the workalong a circle which will be termed the grinding line. If a concavesurface is to be produced, the square end of a solid cylindrical wheelis used.

It will be appreciated that the active cutting edges, whether a singlerotating tool, the teeth of a milling cutter, or the abrasive particlesin a grinding wheel, move in a direction, which is generally transverseto the direction of movement of the surface of the work. This prevents acontinuous ridge or groove being formed in the Work by any irregularityin the tool. Furthermore this means that, in grinding, an extremely highfinish can be obtained, which is not limited by the grain size of thewheel. In fact, the finish can be many times better than the grit ofwheel used, a result which is unapproachable by any other method. Theslower the rotation of the work relative to that of the wheel, thebetter the finish for a given grain size of wheel used.

In one machine according to the invention for carrying out the abovemethod, there are provided on a bed two heads bearing rotating spindles,one carrying the work and the other carrying a grinding or cutting tool.The two axes of rotation lie in a common plane and one of the heads,preferably the cutting or grinding head, can be moved in an are about anaxis perepndicular to that plane, and preferably intersecting the axisof rotation of the tool spindle. The Work head can be displacedhorizontally in a direction perpendicular to its own axis of rotation,for reasons which will become apparent later.

A stop may be provided on the work head which can be swung into linewith the chuck carrying the work, and enables the work to be quickly setto the right position axially. On the grinding head a diamond dressingtool may be provided, swinging in a plane perpendicular to the axis ofrotation of the grinding wheel, and this plane forms a fixed datum fordetermining the grinding line, irrespective of wear of the Wheel.

The machine preferably includes means for automatically advancing thegrinding head rapidly up to the work, feeding'it in slowly, and thenproviding a dwell at the end of the stroke to give a very fine finish tothe work. During the dwell of the grinding wheel, the rotation of thework may be slowed right down.

The invention will now be described more fully with reference to theaccompanying drawings, in which;

is fixed by therelationship:

shape of the head, the required va Figure l shows'diagrammaticallyexamples of the dis position of the work and wheel in the application ofthe invention to grinding;

Figure 2 shows a front elevation of a machine for carrying out themethod of the invention; 7 V p Figure 3 is a scrap section onthe line .3'3 of Figure 2; Figure 4 shows-to a larger scale a section of the workhead on the line .44 of Figure 3; V

Figure '5 shows in detail the reduction in the headstock spindle;

Figure 6 is a scrap View from the left in Figure 1;

Figure 7 is a section to a larger scale of the upper half of thegrinding spindle assembly, taken on the line 7-7 in Figure ,6; a W g a aFigure 8 is a scrap sectional elevation of the grinding gear embodied ofthe grinding head looking head and part of the associated advancingmechanism 7 for the Slide; 7 n r Figure 9 is a sectional eleva'tion ofthe lower part of the grindinglhead.. showing the feed-in mechanism{ andFigure 1-0 is a plan viewof the feed-in mechanism 'with- I in thegrinding head; Z

Referring first to Figure 1(a), thereis shown a hollow cylindricalgrinding wheel 1 'forminga part-spherical en-. larged end;2 on a rod 3.The rod is rotated about its own axis A, and the wheel is independentlyrotated at a higher speed about its axis B. It will be seen that theinner edge of 'theendof the wheel.1 engages the surface of the s'phereona circle which we have called the grind-l ing line, and that, since boththe work and the wheel are rotating about different axes, the spheremust inevitably b'e' 'true, with its centre on the intersection-C of thetwo axes, when thewheel has been fed inyalong its own 7 axisBsufliciently fair for it to corneinto contact with the whole of thesurface of the'end 2;

Normally, the end 2 will have previously been :rnachined or ground Iroughlyto a spherical shape bya form tool or wheel, and

the m ethod according tothe'inventionwill only be used to give a finaltruing cut. 1 J

. In order to ensure that no u means matter a givenradius .of sphericalsurface and V a given diameter of grinding :wheel, the angle a between Ai a where D is the diameterjof the inner edge of the wheel and R is theradius of the sphere to be produced."

nground'portion is left on .theend 2 adjacent the axis of therod 3, itwill be seen that the feed-in of the wheel 1 must end at such a point"that the grinding line just intersects'the axis A. This;

e setting angle,

7 V 4 radii the overhang with s impossibly great. instead, the point F'is fixed, ,and the axis A can be offset laterally from it. This alsoenables the distance K'from the'plane of the grinding 7 line to thepoint F to be fixed independently of the work which, as will be seen,makes it possible to determine extremely accurately the point at whichthe feed-in of the wheel stops and hence the finaldiameter of the work.The otfset of the axis A from F is indicated at O and is given by therelationship:

Figure l(b)' shows the set-up for grindingia ball head large incomparison with the diameter of the rod, and

in Figure its is shown the grinding of a dome of large 7 Whilst inFigure l we'have shown throughout a grinding wheel 1, it will beunderstood that it may equally well be replaced'by a milling cutter, oreven by a'single 7 7 tool rotating about the axis B. If a single tool isused,

however, the rotation of the -wor k must be very slow in comparison tothatjof thetool if a reasonable finish is 'to' be obtained, and theingly long tir'ne.- V v 1 An example of a practicalmachine fol-carryingout the invention, and embodying a number of refinements,

is shown in the remainder of the-drawings; Referring to Figure 2,'themachine comprisesa bed 10,, on which is mounted a headstock il forrotating the work and a table 12 on which the grinding head is mounted;

' The headstock- 11 is mounted ontransverse slides,

one 3/ and one flat, on the bed 10, so -that it can be movedhorizontally in a direction transverse tothegaxis; fot the headstockspindleiS (Figure 3;),"on the .end'of V which is a collet chuck 14forcarrying the work.

The transverse position of the headstock is controlled by a leadscrewactuated by a handle 15 which has a micrometer scale (not shown)and enables the ofisetiO of the axis of rotation of the workti; e. theheadstock J spindle) 'from the focal point to be'controlled veryaccurately. A lever 16 serves toropen 'and close the chuck14. a V V Thebed .10 has its upper surface formed as a quadrant at 17, and thetable'12 is pivoted on a spigot projecting alarge spherical 'end isrequired,or only a dome repre.

senting a small fraction of 'asphere. The setting'angle a .must beatleast half the angle subtended at the centre betweenthe edgegof thesphereand the axis A, which angle iscalled 0. Aconvenient rule to adoptis to make b' /26+5; which gives the cutting edge ofjthe wheel areasonablearc of travel clear'fof the work, to prevent its clogging,Forfexample, in Figure l, *in,which. the

end .Zis slightly less'thana hemisphere, 0 is 89, making 11:45

from u and R For adjustment'of Now if this point F: -we reT-to bejri'zade coincident with C,

, I V V the setting angle, axis B of 1 the grinding heel '1 can beturned about a focal point P,

In these circumstances, a'is fixed by; the

luejof 1) is determifled vertically upwards from the centre of thequadranttthe axis of'the spigot if extended upwards, would pass near thecollet chuck, and its point of intersection with. the 1 horizontalplane. ofthe headstock spindle 13 represents thefocal point F of Figure.1. An arcuate rack or gear segment iS on the bed 10 is engaged by apinion 19 scale to within 15 secondsaofar c.

that it is rigid with the base during actual grinding.

The actual gr-indingl spindle 21 is formed by an V l integral extensionof' the s haft of anelectric motor built intoa housing 22 on a slide 23.This slide 23 is mounted V on 'slideways of generous dimensions .on thetable.12, 'so asto be'i 'movable towardsand away from the focal point;The grinding spindle is in exactly. the sainej horizontal plane as'thework spindle 13 audits '7 passes through the focal point'F (i. e; theintersection a1axis aboutwhich thetable a with thatplane of the vertic12 can be turned).

mall radius work would be I job would take a correspond-.

The headstock 11 carries a stop on the end of an arm 26 pivoted on aspindle 27. A handle 28 enables the stop to be swung down in front ofthe chuck 14 and it may be provided with a micrometer screw to enable itto be moved in the direction of the axis of the headstock spindle. Thisstop enables the work to be set rapidly in the correct axial positionwith respect to the focal point F, due allowance being made for theamount to be ground off.

The interior of the headstock 11 is shown in Figures 4 and 5. At 29 and30 respectively are the V and flat slides on which it is carried on thebase. it will be seen that the lever 16 is secured to a shaft 31carrying lugs 32 on which pins engage an annular groove in a sleeve 33rotating with the headstock spindle 13, to control the axial position ofthe sleeve. This sleeve 33 has a conical surface engaging a pair ofpivoted bell-crank levers 34, which in their turn engage the end of atube 35 running coaxially within the spindle 13 and acting on a splitsleeve 36 containing the jaws 37 of the collet chuck. It will beunderstood that angular movement of the lever 16 opens and closes thejaws of the chuck. The work, of which a typical example is shown at 38,is held in the jaws 37 by means of a split bush 39, which enables theshank of the work to be gripped even though there is a ball head on eachend. An axially sliding plunger as within the sleeve 36 is urgedoutwards by a coil spring 41 and tends to push the works outwards. Thissimplifies setting the axial position of the work, as it is clamped inthe chuck whilst being urged gently against the stop 25, which is thenswung out of the way.

The spindle 13 runs in opposed conical bearings 42 and 43, and carries,keyed to it, a spider 4a (Figure 5) the fingers of which extend betweenballs 45 forming an epicyclic reduction gear between a sun wheel in theform of a V pulley 46 and an annulus 47 formed with a V pulley grooved8. Both the sun and annulus are free to turn on the spindle 13 and theengaging pressure is derived from angularly spaced coil springs 49, thethrust being taken by a ball race 50.

The pulleys 46 and 47 are connected by belts 51 and 52 respectively toseparate electric motors contained in the base it). During normalgrinding the right-hand pulley 48 is stationary and only the left-handpulley 4% is driven, so that the spindle 13 is driven at a lower speedthrough the reduction gear formed by the balls 45. When a very lowrotational speed of the spindle is required, during the dwell as will bedescribed later, the second motor is started up to drive the annulus 4-7in the opposite direction but at a slightly lower speed than the Ipulley 46, and only the difference in speeds is transmitted to the balls4531 Turning now to the grinding head, Figures 6 and 7 show the upperpart of the housing 22, in which is mounted an electric motor 55, itsshaft 56 being mounted in special bearings lubricated by oil mist from aspecial pressure lubricator which has been indicated at 57 in Figure 2but has been omitted from the remainder of the drawings for clarity.This enables the shaft 56 to run up to speeds as high as 24,000 R. P. M.

On the end of the shaft 56 there is screwed a boss 53 carrying acup-shaped grinding wheel 59. A bracket so carries a transparent guard61 to protect the operator from coolant flung oh the wheel.

As mentioned earlier, the housing 22 and slide -3 are movable with resect to the table 12 in the direction of the axis of the grindingspindle. There are two separate mechanisms for effecting the inwardmovement, one for providing a rapid advance up to the work and a finerone for producing a slow feed-in during the actual grinding operation.The first of these mechanisms is shown in Figure 8 and comprises an aircylinder 62 under the control of a solenoid-operated valve actuated froma push button on the bed 10. The cylinder itself is pivoted to the table12 and its movable piston advances a link '15 63 to tilt a motion platedo, forming a toggle linkage with a further link 65 pivoted at 66 to theslide 23, thus advancing the slide rapidly and taking the wheel 59 toWithin a few thousandths of an inch of the work. Figure 9 shows thelinkage in the fully advanced position.

The pivot or about which the plate 64 turns is substantially stationaryduring the rapid advancing motion described above, but is not mounteddirectly on the table 12. On the contrary, it is carried on the top endof a lever 68, of which the upper arm is only one fifth of the length ofthe lower arm. The second of the mechanisms referred to above, forgiving a slow progressive feed-in, is connected via a link 69 to thelower end of the lever 68 and comprises a slide 79 movable on asub-assembly.

'71 within the table 12 and urged to the right in Figure 9 by acompressed air cylinder '72. The rate of movement is controlled by anoil dashpot 73, the piston of which is connected to a piston rod '74screwed into the slide 70. The flow of oil from one side of the pistonto the other takes place through pipes leading to a metering valve 76(shown more clearly in Figure 10), which can be readily adjusted byhand.

Referring now to Figure 10, a link 77 pivotally mounted at one end onthe subassernbly 71 forms at its other end a pivot for a lever '78,which is itself pivoted at its mid-point to the top of the slide 74). Atits free end the lever 78 carries a striker plate 79, which is kept withits face square to the line of movement of the slide by means of amember t) forming a parallel linkage with the lever '78. It will be seenthat the five-to-one magnification of the lever 63 combined with thetwo-toone ratio of the lever 73 gives a linear movement of the strikerplate 79 which is ten times that of the slide 23.

A carriage Si! is mounted for sliding movement on the sub-assembly 71 ina direction parallel with that of the movement of the slide 79. itsposition is adjusted by means of a lead screw under the control of ahand wheel 83 which is provided with a micrometer dial 34 (Figure 9). Astop formed by an electric micro-switch 35 is mounted rigidly on top ofthe carriage 81 in the path of the striker plate 7? and a secondmicro-switch 86 on a carrier 3? is mounted for sliding movement on thecarriage. A spiined shaft 88 actuated by a knob 29 with a micrometersetting dial 9d enables the position of the switch 86 to be altered withrespect to the carriage 3i irrespective of the overall position of thecarriage. Adjustable bolts 91 below the micro-switches form positivedead stops to bring the striker plate '79 to a halt immediately afterthe corresponding micro-switch has been actuated.

As stated earlier, operation of a push button on the base iii opens asolenoid-controlled valve to admit air to the cylinders 62 and 72. Thisis effected through a pipe 92. The quick advance produced by thecylinder 62 is continued as a slow feed-in by the cylinder 72 until thestriker plate 79 engages the micro-switch 86, initiating the action ofan electronic timer which, after a predetermined time delay, admits airto a pipe 93 connected to the exhaust sides of the cylinders to actuatethem in a reverse direction until the plate 79 engages the stop 91 andthe other micro-switch 85. The micro-switch is in series with thestarting button and prevents the next cycle of operations being startedby the operator unless the slide 23 is fully retracted.

A T-junction 94 in the pipe 93 branches ofi to an air cylinder 95, whichapplies air pressure to the fluid in the hydraulic circuit of thedashpot 73 to prevent cavitalien behind the piston on the reversal ofdirection.

it will be seen that the total distance of the slow feedin is controlledby the knob 5%, which fixes the distance apart of the twomicro-switches. The feed-in may be varied over a range from onethousandth up to one quarter of an inch. Once the overall feed-in hasbeen set (this depends on the amount of material to be removed), thewheel to the points at which it starts vantage that the. sphericalstroyed during the course 05 and ends in relation to the focal point;This is deter mined "by the requirement-that the front. face of thewheel59'at the end of the stroke should be rthe distance K of Figurelfrom the focal point i A diamond dressing tool 96 is carried on an arm97 pivoted to a carrier Fe (Figures 2 and 3) on the table 12 to move inan arc in a vertical plane under the influence of a control handle Thediamond'is traversed'across the faceo f the wheeld'e with the slide 23inits fully retracted position. i

The final forward position of the wheel, i. e. its position during thedwellyshc uldbe such that the face of the wheel is the fixed distance Kfrom the focal point P. If there were no slow feedin, this would simplybe fixed by the foremost position of the rapid advance, but, with the'additional'slow feedin, this final position. will be the total rapidadvance. it includes a micrometer screw which enables the plane of thediamond .to be set by a predetermined ount beyond that plane (in adirection away from the V V V to the feed-in set by the ltnob Then,provided the knob fi'is not disturbed, this serves as a datum for allsubsequent operations on the particular batch of work be'ing ground, as,whcn the grinding wheel 59 wears, the Wheel Slis turned by the operator:to advance the carriage a l a few thousandths of an inch and the wheelis trimmed by the diamond in the fully retracted. position.

Then, on the next feed-in the wheel stops withits newly dressed face atexactly the planerat which the previous face stopped before. V V iThe'length of time or the feed-in and of the dwell will dep hid upon thesize, material and centre angle of the sphere to be ground, also on thegrade and grit of the wheel and the amount of material left on theworlrpiece for removal.

During the dwell the speed be brought right down.

of rotation of the work may 4 R. l M. during a dwell or" about oneminute. By' this. means it has be found possible to achieve an extremelyhigh surface inches, which is better than could be achieved'by ordinarylapping. This is chiefly attributable to the fact that thedirection ofmovement of the cutting edges on the be attached to the arm 92- of thetotal a slot) which distance is made equal 7 sh, of as little as one andahall micro forward of the foremost position of the rapid advance bysaid first spindle for retaining a'work-piece, asecond rotatablespindle, cutting means carried on said second spindle; "sa'd cuttingmeans-being displaced "from the axis of d second spindle and defining acircular path about said axisg said first andsecond's pindles lying in acommoii plane, means] for causing relative angular movement between saidspindles about an axi s'perpendicular" to said plane, means foradvancing said second spindle along itsown axis of rotation up to thepoint where said circular path intersects the axis of rotation of: saidfirst spindle: V 7

2. Apparatus for producing a spherical surface on a work-piececomprisinga bed, a hcadstoclcon said bed, a' first rotatable spindle, said firstspindle being mounted for" about a horizontal axis in said'headstock,world 1 n g means on said first spindle, a table, s'aid table beingmounted on said bed for angular 'r'novem'dnt' about" a vertical axis, aslide on said table, said'slicle being rccip rocable horizontally in adirect'ion passing through; said vertical axis, a second rotatablespindle, said second spindle being mounted for rotation on said slideabout a a horizontal axis intersecting said vertical axis,;a cuttingtool mounted on said second spindle and definingin its' rotation acircular path, means for causing rotationof.

said first and second spindles and means for advancing;

cage, and including ineans for driving said'annulus'in directionopposite to that of said sun wheel.

5. Apparatus according to claim 2, wherein said means for advancingttheslide comprises a first means for pro-T ducing a rapid'advancc, inconjunction with a second means for producing an additional slowfeed-in.

V g In one example the work is rotated at 25 R. l. M. during the feed-inand then at only i the axis of rotation of said motor spindle beinghorizontal, f

tool (in this case'the abrasive particles in the grinding wheel) issubstantially transverse to that of the surface of the work itself. 7

It will be appreciated that the load on the bearings of' w "axial, sothat there is no the grinding spindle is tendency forsideways play todevelop. 7 Itshould also be noted that the truthof the sphere is notailected by any. rror'in the concentricity of the 'collet chuck, since IV the centre of the sphere willelwa'ys lie on th'eaxis of rotationofithe worlgirrespective of the position of the axis of the-work itself. 1g V V V To'ov ercorne difiiculties in getting coolant to penetrateinside the cup grinding wheel, theiwheel may be of a special impregnatedself-lubricating;kind. Themachine described may also be used forlapping, and has the ad rm of the work is not dethe lapping operationl Iclaim: 7 a V V V 1. Appairatusfor producing a'spherical surface on a Vwork-piece comprising a first rotatable spindle, means on f iusaidSpindle,

6. A machine for producing a spherical surface on a bed for angularmovement about a vertical axis, a worl f carrying spindle mounted forrotation about a horizontal i axis in said headstock perpendicularto'the direction of sliding of said headstock on the bed, a firstelcctric'rnotor, means for driving said work-carrying spindle from saidfirst motor, .a' slide mounted for sliding movement on said} table in ahori sontal direction passing through said verti-g cal axis, an electricmotor on said slide having a spindle,

motor spindle, said grinding wheel defining a circular pathi vanc ingsaid slide slowly, and meansfor stopping the ad Vance at the point wheresaid circular path intersects the axis of said work carrying spindle. ii a 7. Amachine according to claim 6, wherein said meansfor stopping theadvance of the. slide is adjustableinf position; V a i ."8..A machine.for producing a spherical surface on:

c'agefsaid first spindle being connected to said planetj 7' a work-piececomprising a bed, a headstockmoufitedf on said bed, a work-carryingspindle mouhte'd'for rotation;

in said headstock, power. means for driving said Worki:

on 1 said table, a grinding sp'indle mounted 'for rotation" saidspindles having their axes intersecting and lying in slide, lpower meansTfordriving said grinding;

a' common planegthe axis'of said pivotal con-if nection intersectingthat of said grinding spindle, and being furthermore perpendicular tosaid common plane, means for clamping said pivotal connection, agrinding wheel carried on said grinding spindle, said grinding wheelhaving a plane end face and a cylindrical surface, the intersection ofsaid face and surface defining a line herein termed the grinding line,means for advancing said slide with respect to said table in a directionparallel with the axis of rotation of said grinding spindle, and meansfor halting its advance at the point where said grinding line intersectsthe axis of rotation of said work-carrying spindle.

9. A machine as claimed in claim 8, including a diamond dresser, saiddiamond dresser being mounted on said slide for movement in a planewhich is perpendicular to the axis of said grinding spindle and is afixed distance from the axis of said pivotal connection.

10. A machine as claimed in claim 8, wherein said means for advancingsaid slide comprise a first pneumatic motor on said table, a togglelinkage, pivotal connections between said motor and linkage and betweensaid linkage and said slide, a second pneumatic motor on said table, anda lever interconnecting said second motor and said toggle linkage.

l1. A machine as claimed in claim 8 wherein the axes of saidwork-carrying and grinding spindles lie in a horizontal plane and theaxis of said pivotal connection is vertical.

References Cited in the file of this patent UNITED STATES PATENTS1,617,167 Schramm Feb. 8, 1927 1,994,529 Meyer 1. Mar. 19, 19352,286,361 Goddu June 16, 1942 2,424,271 Galloway July 22, 1947 2,629,975Desenberg Mar. 3, 1953

